Bar for reinforcing materials

ABSTRACT

Reinforcing composite bar ( 1 ) for reinforcing materials ( 5 ) such as concrete, the rod ( 1 ) being made from continous fibers and a matrix material. The bar ( 1 ) is of rectangular, preferably square shape with runded corners. One or more of the sides of the bar may be provided with longitudinal continuing bands ( 3 ). The width of the respective band ( 3 ) may be more than ⅓ of the total width of the sides, and the dept of the respective band ( 3 ) may be more than {fraction (1/50)} of the width of the same.

The present invention ralates to a reinforcing composite rod or bar for reinforcing materials such as concrete, the rod being made from continous fibers and a matrix material.

The reinforcing bar may be formed in a forming process by pultruding, extrusion or moulding, or a combination of these, of continuous fibres and matrix (resin) in a one-line process or in combination with a second-line process, forming a surface texture and geometry designed specially to achieve sufficient bond to the materials which to be strengthen. Materials that could be strengthen by use of the bars are like metals, concrete, wood, plastic, stone, ceramic. The surface is divided into texture zones of corners and sideband, and depending on the radiuses and widths respectively, the geometry can be varied and specialised and geared to the product to be strengthen. The bar is made in the forming process with at least 50% reinforcing fibres by weight and a matrix which impregnates the fibres through a bath, spray injection or pressure. The surface texture is applied in the forming process line by use of rip off sheet, mechanically by rollers or continuous running bands in or outside the tool(s) for forming and curing of the bars. The texture surface of the bars can also be applied as an external layer in a separate process of moulding, extruding or pultrusion, after which the geometry of the bar is formed in the main forming process as described above.

Composite bars of the above type is used for the strengthening and stiffening of different products and constructions made of materials like metal, concrete, wood, plastics, stone, ceramic and combinations of these where sufficient bond between the bars and materials is required to achieve structural functionality. Many reinforced products made of metals, concrete, wood, plastic, composites, stone and ceramics, require optimisation on slenderness, weight, size and cost, but this is often obtained on account of strength, stiffness or by becoming susceptible to oxidation such as steel and other metals causing problems with corrosion, discoloration and thereby loss of structural strength. In some cases where metals are used to strengthen or stiffening the products there are problems with elongation or variation in material physical behaviour that cause cracking or insufficient bond between the product's material and the strengthening elements, i.e. the reinforcing bars.

The reinforcing material according to the present invention is a continuous fibre and matrix composite often called FRP (Fibre Reinforced Polymer) which is being used in a variety of construction materials due to excellent and flexible physical material properties such as high specific strength, light weight, none or low electric conductivity, non-magnetic properties, high resistance against acids and chlorides or aggressive environments, as well as formability and shaping.

As stated above, steel and metals in general are susceptible to oxidation which cause corrosion of and rust on ferrous metals due to hydroxides of iron and oxides from atmospheric oxygen in the presence of water. As long as the pH is maintained at high alkalinity (pH 12-14) and in combination with very good poured concrete quality, the steel keep passive leading. To low pH, low concrete quality, insufficient product quality, poor execution of work, or exposure to strong acid can cause penetration of the protecting concrete zone that should protect the steel reinforcement rebar, i.e. chlorine ions from salt contaminated aggregates, road salt, marine environmental, seawater, carbonisation, access to CO₂, access to oxygen, and moisture. Furthermore, conditions which may result in chemical deterioration of the concrete, i.e. by sulphate or acid attack, or mechanical deterioration of the concrete from freezing and thawing in a wet or moist condition, may in turn cause rust and corrosion of the steel reinforcement, cracking of the concrete and loss of structural strength. When the reinforcement start corroding (rusting), the ferrous oxide will expand and cracks are initiated in the concrete due to internal stresses caused by the rust. Concrete will fall off and the steel rebars will be exposed to the atmosphere and the environment that caused the corrosion process, the speed of the process will further increase and the structure will be loosing structural strength and may in worst case collapse. Controlling these parameters is difficult and substantial economical and structural problems for concrete structures is caused all over the world. Due to lack of other alternative strengthening materials, steel reinforcement bars often have been misused in concrete structures.

As stated above, composite reinforcement bars are previously known and have been used to a minor extent. Such known bars are, however, encumbered with a major disadvantage, namely the poor bonding between the product's material (concrete) and the strengthening bar (FRP-bar), The fact that traditional bars are designed with a circular shape makes it difficult to provide the surface with the required roughness.

With the present invention is provided a composite reinforcing bar with excellent bonding properties and where the reguired surface roughness is provided in a simpel and cheap manner.

The invention is characterized in that the bar is of rectangular, preferably square shape with runded corners, as defined in the attached claim 1. The sides of the bars may have recesses to increase surface area and bonding.

Further, a method according to the invention is characterized in that the fibers are impregnated through a bath of resin or throug injection or by pasing through a spraying zone whereby the bar is formed in a forming process, as defined in claim 7.

Dependent claims 2-6 and 8-9 define preferred embodyments of the invention.

The invention will now be described in further detail and with reference to the drawings, where

FIG. 1 shows a vertical sectional view of a short piece of a bar according to the invention being partly embedded in a concrete,

FIG. 2 a) shows, in larger scale, a cross sectional view of the inventive bar,

FIG. 2 b) and 2 c) shows side views (of a piece) of the same bar, and

FIG. 3 shows a side view of a piece of a bar with a specifc surface texture pattern.

FIG. 4 shows tables with an overview of different dents or recesses respectively depths of such dents or recesses used in the surface texture patterns.

The reinforcement bar is intended to be used as strengthening element in constructions or products of any kind of material. The bar may be moulded, cured or glued together with any type of other material i.e. but not limited to, concrete structures, wooden structures or elements, any type of plastic products or constructions, structures or products made of metals, or any materials of that kind that need to be strengthen of economic or structural reasons.

The reinforcement bar (1) according to the present invention, may comprise a mixture in any combination of continuous fibres made of glass, carbon, aramid, polyester, ceramic, syntetical fibers, natural fibres or similar, but not limited to these, together with any type of resin systems like thermoplastic resins and thermoset resins which are impregnating the fibres. The reinforcement bar (1) shown in FIGS. 1-3 has a rectangular shape with rounded corners (2) and with continuing bands (3) along each of its sides.

The composite bar is preferably manufactured of fibres which are impregnated through a bath of a resin or through a injection system where the fibres are sprinkled with a resin system and then formed in the forming process where the fibres and the resin are glued and cured together to the requested geometry, and with the specified outer texture of dents or recesses which may have been mechanically penetrated into the surface, moulded or extruded to the outer surface of the bar and or formed by print off a peel-ply texture or similar on the outer surface.

The cross section of the reinforcement bar is shown in FIG. 2. The reinforcement bar according to the invention is designed with rounded corners (corner₁₋₄), each being defined by an angle (ang₁₋₄) and a radius (r₁₋₄), and longitudinal side bands (bands₁₋₄) that may have defined depths (d₁₋₄). By combining these parameters the reinforcement bar can be specified and specialized for the intended application. One further unique design feature of the reinforcement bar according to the invention is the external surface texture and the way that this texture is provided on the bar, as described above. The surface texture defines a roughness which will give sufficient bond between the reinforcement bar and the main material to be strengthened. The intention is to use the bars as the strengthening and the reinforcing element of structures and of products where forces from external loads or internal strains will be transfered to internal stresses in the main product material and in the bars.

This invention makes it possible to produce a reinforcement bar product with a geometry and a roughness as required and defined by testing of the main product, or in accordance with requirements in any design codes or standard defined for its kind, purpose or application. This roughness, i.e. the dents or recesses and their depths, is attained when the parameters defined in FIG. 2 are varied within the range defined in Table 1 below to attain the geometry suited for the reguired product. TABLE 1 Geometry Parameters d₁₋₄ [mm] corner₁₋₄ band₁₋₄ [mm] [mm] r₁₋₄ [mm] ang₁₋₄ [grad] [mm] 0.1-5 1-25 0-90 2-50

The roughness can be applied on the curved corners, corners₁₋₄, the sideway band, band₁₋₄, separately or in any combination. The roughness must be defined and applied in accordance with the area of application and in accordance with the necessary requirements of the roughness. The roughness may, as an example, be chosen with a pattern as is shown in FIG. 3, which defines a system for a principle on how to apply and arrange the location of the centroids (centre of gravity) of the dents or recesses shape types, shown in FIG. 4, defined by three lengths, I₁₋₃ and the angle, θ. The three lengths and the angle forms a triangle where the corners represent the location of the centroids of the dents/recesses which will form the texture pattern shown in FIG. 3 and in FIG. 4.

The variation of the lengths, I₁₋₃ and the angle, θ is shown in Table 2 below. TABLE 2 Texture Type Parameters I₁₋₃ [mm] θ [grad] Depth of Pattern [mm] 1-20 10-90 0.1-5

The roughness, i.e. the texture pattern of the depressions, may be attained, as described above, by stamping, imprinting, impressing, copy printing of peel-ply texture pattern, texture film, moulding, extrusion or similar. The depth must be defined from testing and calculations to achieve the correct bond between the material of the product or structure and the reinforcement bar and may be adjusted and specialized in each case where it is used.

FIG. 4, uppermost and lowermost tables shows examples of designs related to the shapes and depths respectively of the depressions, dents or recesses of the surface texture patterns according to the invention. It should be stressed, however, that the invention is not limited to such designs. Thus the texture patterns and dents or recesses may be of any preferred design and may have different depths, widths and angles than what is shown and described above. 

1-9. (canceled)
 10. Reinforcing composite bar (1) for reinforcing materials (5) such as concrete, the rod (1) being made from continuous fibers and a matrix material, wherein the bar (1) is of rectangular, preferably square shape with rounded corners.
 11. Reinforcing bar according to claim 10, wherein one or more of the sides of the bar are provided with longitudinal continuing bands (3).
 12. Reinforcing bar according to claim 10, wherein the width of the respective band (3) is more than ⅓ of the total width of the sides.
 13. Reinforcing bar according to claim 10, wherein the depth of the respective band (3) is more than {fraction (1/50)} of the width of the same.
 14. Reinforcing bar according to claim 10, wherein the surfaces of the corners and/or the sides of the rod are provided with a multiplicity of depressions, dents or recesses formed in a texture.
 15. Reinforcing bar according to claim 14, wherein the texture have ribs, dots, circular, square, triangle or eliptic shape.
 16. Method of producing a reinforcing bar made of composite matrix material with continuous fibers, wherein the fibers are impregnated through a bath of resin, spray injection, through pressure, or any combination of these manufacturing methods, whereby the bar is formed in a forming process by moulding, pultrusion, pull-winding or extrusion.
 17. Method according to claim 16, wherein textures are provided on the surface of the bar in one step by use of pressure and means of rollers, sheet or continuous running bands having beads on the surface corresponding to the required texture on the bar.
 18. Method according to claim 17, wherein textures can be provided on the surface of the bar in a separate process of moulding, extrusion or pultrusion.
 19. Reinforcing bar according to claim 11, wherein the width of the respective band (3) is more than ⅓ of the total width of the sides.
 20. Reinforcing bar according to claim 11, wherein the depth of the respective band (3) is more than {fraction (1/50)} of the width of the same.
 21. Reinforcing bar according to claim 12, wherein the depth of the respective band (3) is more than {fraction (1/50)} of the width of the same.
 22. Reinforcing bar according to claim 11, wherein the surfaces of the corners and/or the sides of the rod are provided with a multiplicity of depressions, dents or recesses formed in a texture.
 23. Reinforcing bar according to claim 12, wherein the surfaces of the corners and/or the sides of the rod are provided with a multiplicity of depressions, dents or recesses formed in a texture.
 24. Reinforcing bar according to claim 13, wherein the surfaces of the corners and/or the sides of the rod are provided with a multiplicity of depressions, dents or recesses formed in a texture. 